1. Field of the Invention
The invention relates to a turbojet-engine exhaust nozzle.
2. Related Art
More specifically the invention relates to an axisymmetric, converging-diverging exhaust nozzle of which the diverging portion situated downstream of the converging portion can be swiveled relative to the turbojet-engine axis, said diverging portion comprising a plurality of diverging flaps hinging upstream on the downstream ends of the converging flaps and hinging downstream on linkrods connected to a vectoring ring of which the axial displacement and the tipping movement are controlled by a plurality of linear actuators anchored in a stationary structure, guide means being present to guide the vectoring ring relative to the stationary structure while it is moving.
Swiveling nozzles impart additional agility and improved manoeuverability in pitch and yaw to combat aircraft. In some designs, the unit and the converging-diverging nozzle are mounted in swiveling manner on a spherical element. In other designs, which offer weight reduction, only the diverging nozzle portion pivots by means of a vectoring ring.
The French patent document 2,645,593 A discloses a nozzle of which the vectoring ring, which is driven by three control actuators equidistant from one another by 120xc2x0, is mounted on the structure by three axial rods equidistant from each other by 120xc2x0 which can slide in supports firmly affixed to relatively stationary structure. The rods are connected by swivels to the ring. If the guide length of the slide bearings is inadequate, the radial forces applied to the rod end generate a tipping torque that may jam the rod during its translation.
The patent document WO 92/03649 fits the vectoring ring with three radial stubs equidistant form each other by 120xc2x0 about the axis and sliding in axial apertures between pairs of parallel rails which are solidly joined to the stationary structure and of which the center planes intersect along the turbojet-engine axis. Using this design, the center of the vectoring ring defined by the intersection of the stub axes is ideally situated on the turbojet-engine axis. However the pressure-generated radial torques in the link between the stubs may entail deleterious friction for the jet-deviation position. Said document reflects the nearest state of the art to the present invention.
One of the objects of the present invention is to reliably provide a guide means for a vectoring ring fitted with three rails that shall be jam-free while also assuring axial translation of the ring.
The invention solves this problem in that the guides of the vectoring ring comprise three axial apertures which are each situated in a base firmly joined to the stationary structure and of which the center planes intersect along the turbojet-engine axis, the side walls bounding said apertures acting as guides for three spherical rollers fastened to radial stubs firmly affixed to the vectoring ring and equidistant form each other.
Accordingly, the roller centers are situated in the center planes of the apertures and the axial resultant of the differential pressures due to jet deviation is tangentially applied to the contact joints of the spherical rollers and the side walls of the apertures, thereby eliminating undesired radial torques.
Advantageously the linear control actuators are connected by swivels to the vectoring ring and to the stationary structure. Therefore the absorption of the tangential component of the differential pressures does not affect at all the linear control actuators.
Preferably the radial stubs extend inside the vectoring ring.
To distribute the tangential forces over a larger rest area, each spherical roller preferably is mounted in a corresponding aperture with insertion of a first slide sliding axially along the side walls of said aperture and of a second slide sliding radially on the first slide, said roller being spherically linked to said second slide.
Advantageously the first slide is fitted with a radial orifice receiving in a sliding manner the second slide.